Measles
麻疹
Epidemiology:
Global Prevalence: Measles is found worldwide, but its prevalence varies geographically. Before widespread vaccination, measles was nearly universal in childhood. Since the introduction of the vaccine in the 1960s, significant progress has been made in reducing measles cases and deaths. However, measles remains endemic in many parts of the world, especially in developing countries with limited access to vaccination programs.
Transmission Routes: Measles primarily spreads through respiratory droplets. Infected individuals can transmit the virus to others through coughing, sneezing, or direct contact with nasal or throat secretions. The virus can survive in the air or on surfaces for up to two hours, making it highly contagious.
Affected Populations: Measles primarily affects children, particularly those who have not received the vaccine. However, individuals of any age, including adults, can contract measles if they have not been immunized or have not previously had the infection. Infants who are too young to receive the vaccine and individuals with weakened immune systems are particularly vulnerable.
Key Statistics: Prior to widespread vaccination, measles caused approximately 2-3 million deaths annually. However, thanks to global immunization efforts, this number has significantly decreased over the years. In 2019, the World Health Organization (WHO) estimated approximately 207,500 measles deaths worldwide, equivalent to approximately 567 deaths per day or 24 deaths per hour.
Historical Context and Discovery: Measles has been known for centuries. Ancient Chinese, Persian, and Arabian texts described the symptoms of measles as early as the 9th century. However, the first formal description of the disease was made by the Persian physician Rhazes in the 10th century. The virus responsible for measles was not discovered until 1954 by American physician Thomas Huckle Weller and colleagues.
Major Risk Factors:
1. Lack of Vaccination: The primary risk factor for contracting measles is the absence of vaccination. Unvaccinated individuals who come into contact with the virus are highly susceptible to infection.
2. Travel to Endemic Areas: Traveling to regions with active measles transmission increases the risk of contracting the disease. Unvaccinated individuals traveling to countries with low immunization rates or ongoing outbreaks are particularly vulnerable.
3. Lack of Healthcare Infrastructure: Limited access to healthcare services, particularly in developing countries, contributes to low immunization rates and increases the risk of measles outbreaks.
Impact on Regions and Populations:
Prevalence Rates: The prevalence of measles varies globally. Regions such as Africa, Southeast Asia, and the Western Pacific have higher incidence rates compared to countries with robust vaccination programs. In contrast, regions like the Americas, Europe, and the Eastern Mediterranean have achieved significant reductions in measles cases, primarily due to vaccination efforts.
Affected Demographics: Measles can affect individuals of any age and demographic; however, outbreaks often occur in populations with lower vaccine coverage. These include communities with vaccine hesitancy, marginalized populations, and areas with weak healthcare infrastructure. Additionally, overcrowded settings such as refugee camps and schools can facilitate rapid measles transmission.
In conclusion, measles is a highly contagious viral infection that remains a significant global public health concern. Although vaccination has dramatically reduced measles cases and deaths, outbreaks still occur, particularly in regions with limited access to immunization programs. Lack of vaccination, travel to endemic areas, and limited healthcare infrastructure are the primary risk factors for measles transmission. Efforts to increase vaccination coverage and strengthen healthcare systems are essential to further control and prevent the spread of measles.